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Organic Shell (organic + shell)
Selected AbstractsAu@pNIPAM Thermosensitive Nanostructures: Control over Shell Cross-linking, Overall Dimensions, and Core GrowthADVANCED FUNCTIONAL MATERIALS, Issue 19 2009Rafael Contreras-Cáceres Abstract Thermoresponsive nanocomposites comprising a gold nanoparticle core and a poly(N -isopropylacrylamide) (pNIPAM) shell are synthesized by grafting the gold nanoparticle surface with polystyrene, which allows the coating of an inorganic core with an organic shell. Through careful control of the experimental conditions, the pNIPAM shell cross-linking density can be varied, and in turn its porosity and stiffness, as well as shell thickness from a few to a few hundred nanometers is tuned. The characterization of these core,shell systems is carried out by photon-correlation spectroscopy, transmission electron microscopy, and atomic force microscopy. Additionally, the porous pNIPAM shells are found to modulate the catalytic activity, which is demonstrated through the seeded growth of gold cores, either retaining the initial spherical shape or developing a branched morphology. The nanocomposites also present thermally modulated optical properties because of temperature-induced local changes of the refractive index surrounding the gold cores. [source] The problem of similarity: analysis of repeated patterns of microsculpture on gastropod larval shellsINVERTEBRATE BIOLOGY, Issue 3 2004Carole S. Hickman Abstract. The problem of similarity is one of explaining the causes of striking resemblances between patterns and architectural themes that recur in organisms at various scales of biological organization. Classical explanations that have considered only the alternatives of homology and analogy overlook similarities of form that are primarily a consequence of fabrication, conveying little information about evolutionary relationships or functional role. When viewed at successively higher magnifications and when mapped onto a phylogeny, patterns of delicate cancellate microsculpture and granular microprotuberances on the surfaces of larval shells of marine gastropods fail to meet the predictions of exclusively historical or exclusively functional explanations, but are shown to be rich in fabricational information. Similar patterns suggest that early biomineralization of the initial organic shell is under weaker biological control than the processes that modulate assembly of the multi-layered, hierarchically-organized composite materials of the adult shell. Some patterns suggest remote biomineralization, without direct influence of living tissue. Scanning electron microscopy of larval shell features reveals previously undetected variation on basic themes that may have implications for the traditional disciplines of systematics, functional morphology, and fabricational morphology. The integration of the approaches of the traditional divisions of biology is required for full explanation of similarity and to generate a unified set of principles for the analysis of form in living and fossil organisms. [source] Study of ferrite ferrofluids by small-angle scattering of polarized neutronsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Massimo Bonini Nanoparticles consisting of a magnetic core (Fe3O4, CoFe2O4 and CuFe2O4) and a hydrophobic shell were prepared by chemical co-precipitation of the inorganic cores and by subsequently modifying the surface with dodecanoic acid. The nanoparticles were then dispersed in cyclohexane to form stable ferrofluids. These dispersions were investigated by small-angle scattering of polarized neutrons and the data were interpreted according to a `pearl-necklace' model, opportunely modified to account for the core,shell structure of the particles. Results of the fitting show that the particles consist of a magnetic core with a mean radius of 40,50,Å and an organic shell with a thickness of 7,8,Å. These nanoparticles assemble in fractal aggregates when a magnetic field is applied. [source] Electronic and Magnetic Properties of Ligand-Free FePt Nanoparticles,ADVANCED MATERIALS, Issue 5 2005H.-G. Boyen Ligand-free FePt nanoparticles are prepared in densely packed arrays (see Figure) under ultrahigh vacuum conditions, in which oxygen and hydrogen plasmas are used to remove the organic shells that are present after particle synthesis. The electronic structure and magnetic properties of the "bare", face-centered-cubic FePt particles are presented. Applications in high-density magnetic data recording are foreseen. [source] | ||||||||||